Heretofore, there has been provided ultrasonic sensors configured to transmit ultrasonic waves and also to receive ultrasonic waves that are reflected from an obstacle. An example of this type of the ultrasonic sensors is a Doppler sensor that judges presence/absence of an obstacle based on Doppler shift in received ultrasonic waves.
Further, as the ultrasonic sensor described above, there is an ultrasonic sensor that is used in a state in which the ultrasonic sensor is attached to a bumper 1 of an automobile (refer to JP 2010-194441A, for example), as shown in FIG. 43.
In more detail, the ultrasonic sensor in FIG. 43 is fixed to a bumper 1 in a state of being inserted in an exposure hole 11 provided in the bumper 1. The ultrasonic sensor includes an outside block 91 that is inserted in the exposure hole 11 from the outside-face side of the bumper 1 (left side in FIG. 43) and an inside block 92 that is coupled to the outside block 91 from the inside-face side of the bumper 1 (right side in FIG. 43). That is, the ultrasonic sensor is attached to the bumper 1 by the outside block 91 and the inside block 92 being coupled so as to sandwich the bumper 1 therebetween.
However, in a structure in which the bumper 1 is sandwiched between the outside block 91 and the inside block 92 as shown in FIG. 43, since a part of the outside block 91 protrudes from the outside-face of the bumper 1 (left side in FIG. 43), the appearance in a state in which the ultrasonic sensor is attached to the bumper 1 is not good. Moreover, due to the structure in which a part of the outside block 91 inevitably protrudes from the outside-face of the bumper 1, the outside block 91 may be damaged when the bumper 1 comes into contact with an obstacle or the like.